1. Field of the Invention
This invention relates to a clutch release bearing device used to release a clutch in an automobile or the like.
2. Description of the Prior Art
A clutch release bearing device of the type which includes a clutch release bearing, bearing retaining means for retaining the bearing in a predetermined state and biasing means for urging the bearing against the bearing retaining means is known, for example, from British Pat. No. 1,382,354. In the bearing device of this type, the bearing retaining means comprises a driving member made of synthetic resin including a cylindrical portion positioned inside an inner race and a portion extending radially outwardly from the cylindrical portion on one side of the inner and outer races. The operating force for clutch releasing operation is transmitted to a diaphragm spring through the bearing by a fork member bearing against the radially extending portion of the driving member and moving the driving member axially on a fixed guide member.
The driving member effects the operation as described above and therefore, its cylindrical portion is required to abound in slidability, while the radially extending portion is required to be high in strength and small in variation with time. To meet these two requirements, in the above-described example of the prior art, the entire driving member has been formed of synthetic resin containing glass fiber and further, a metal plate (anvil) has been embedded in a region opposed to a fork operating member.
By doing so, the requirements have been nearly satisfied with regard to the radially extending portion, but yet a problem is left to be solved with regard to the cylindrical portion. The problem is that since the cylindrical portion is formed of synthetic resin containing glass fiber, the glass fiber is exposed to the surface and abrades the guide member to hamper the clutch operation even if the cylindrical portion is lubricated. For all that, a material excellent in both slidability and rigidity is costly and difficult to mold.